1. Field of the Invention
The present invention relates to an ink composition (hereafter referred to simply as "ink") which can achieve both high-precise color images and reliability, and to a color ink-jet recording method for conducting a recording making use of the aforementioned ink.
2. Related Background Art
In recent years, the aspects of lowering running costs in ink-jet printers and also reducing the amount of refuse produced thereby have called for a type of recording apparatus in which an ink tank is set separate from a printing head, so that the ink tank alone can be replaced. Such apparatus have already been utilized to a certain extent.
However, it has been found that, in a recording apparatus in which only the ink tank is replaced, problems may occur as follows: Namely, air exists in nozzles and ink passages of the ink tank when it is replaced. And therefore, there may occur an inconvenience that such air may remain in the tank, in the form of bubbles, when a new ink is set thereto. Particularly, with ink-jet recording systems which use pressure pulses as the force for forming droplets, the bubbles which remain fixed within the ink will cause serious problems on a subsequent droplet formation.
Moreover, development of high-density printing heads for color ink-Jet recording apparatus has progressed so that devices capable of high-quality printing have been prepared. However, there are problems with the ink to be used in such devices, since increasingly smaller droplets of ink (in a range of 3 to 50 picoliters per droplet) must be ejected in a stable and controlled manner at high frequencies, in order to conduct high-quality recording, which presents a problem in dynamics. Further, there is a problem with the reliability of such ink, as the ink must not plug up nozzles, nor remain as a residue on a surface of nozzles, and must be able to be controlled at an increasingly higher level in the apparatus.
Solving such problems can never be hoped for if ink material development is only conducted as an extension of past ink material design, while the devices themselves are being designed and provided with functions for high-quality recording. It is necessary to combine various constituent materials having various functions, in a highly skilled manner, in order to provide for an ink which satisfies the various properties required therefor. Specifically, selection and combination of various materials such as substances for protecting nozzles from clogging by an ink (evaporation prevention), solvents for maintaining an ink at low viscosity and for maintaining a long term stability of solution, solvents capable of dissolving dyes in the ink, anti-foaming agents, and the like, are extremely important.